1. Field of the Invention
The invention relates to a turbomachine having a shaft mounted in a shaft housing, and at least one rotor disposed in a rotor housing, overhung at one end of the shaft, for compression, expansion, or transport of a working gas. The bearings have a connector to a compressed gas line that is connected with the pressure region of the turbomachine. A portion of the working gas that is passed from the pressure region through the compressed gas line is applied to the bearings, and the shaft housing has a ventilation connection. The turbomachine can be used, for example, as a compressor, expander, or also as a combined compressor/expander arrangement, for various gas processes such as gas treatment, gas purification, energy production, and, in particular, cryogenic air fractionation.
2. The Prior Art
A turbocompressor for high-temperature applications is described in U.S. Pat. No. 4,786,238, wherein the shaft is mounted in the shaft housing axially and radially by means of hydrodynamic, gas-lubricated bearings. The bearing effect is achieved in that bearing gaps remain between bearing surfaces of shaft housing and shaft that are assigned to one another, which gaps are typically a few micrometers wide. The hydrodynamic bearings, which are also referred to as aerodynamic bearings in the case of lubrication with air, take advantage of the effect of self-lubrication. A slide film is formed hydrodynamically between the bearing surfaces that are assigned to one another, at a sufficiently high relative velocity. In order to implement as small a bearing gap as possible, the hydrodynamic bearings described in U.S. Pat. No. 4,786,238 have bearing shell structures that are resilient, i.e. make resilient contact, and deform and adapt automatically under the lubricant film pressure that is in effect. For cooling the bearings, these can have a slight gas stream applied to them. However, this gas exchange does not lead to any change in the bearing properties. Since the lubricant effect only starts at a high speed of rotation, a slide coating of the bearing surfaces that are assigned to one another is provided in the case of the embodiment described. This coating reduces the friction of the bearing surfaces that are in frictional contact with one another, in certain segments, when the turbomachine is started up. Hydrodynamic bearings are sensitive to pressure surge stresses, which are unavoidable in the case of disruptions or load changes, for example. Because of the slight bearing gap, direct material contact of the bearing surfaces assigned to one another can occur at high speeds of rotation, thereby making it possible for the sensitive bearing surfaces to be destroyed and making a replacement of the bearing necessary.
A turbocharger of an internal combustion engine having a gas-static and gas-dynamic bearing is described in German Patent No. DE 87 17 441 U1. In the case of such a turbocharger for internal combustion engines, with which a pressure increase of about 1 bar is generally achieved, the running behavior is supposed to be improved. For this purpose, a gas-static and gas-dynamic radial bearing is provided, which has spring elements that are arranged in overlapping manner and spread out as bearing surfaces. Because of the low pressure difference generated by the turbocharger and the bearing surfaces formed by the spring elements, which can elastically lie against the rotor, radial bearing of the shaft takes place almost exclusively hydrodynamically at high speeds of rotation. The arrangement, which is intended as a turbocharger for internal combustion engines, is therefore sensitive to pressure surge stresses.